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Warning: Mounting Transmitters


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#1 chris fawcett

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Posted 17 November 2009 - 10:26 AM

Thanks to Robin Thwaites for pointing this out, to Jerry Holway for helping to prepare this, and to Rob Orf for correcting it.

Transmitter manufacturers, among others, are increasingly adopting the Sony V-Mount battery standard to solve two problems at once. That of securely mounting an accessory to a video camera, and of powering it. This usually means mounting a TX directly onto a camera battery plate, then sandwiching the TX between the camera and the battery.

With Steadicam, a TX is usually best placed on the camera, but occasionally—for weight issues, or if the rig is in low-mode—we may want to mount the TX on a Steadicam battery plate. This can be hazardous. Most rigs with more than one battery plate have a switch that changes two batteries from parallel to series. It’s an easy and efficient way to generate 24 volts, but means that placing a TX on the wrong Steadicam battery plate may fry the camera, the rig, or the TX.

Let’s call the battery plates used to power the rig plate A and plate B. In 12V mode A and B are in parallel. In 24V mode, they are in series: A will connect to ground and +12V, B will connect to +12V and +24V. If you don’t have a meter, you can tell which plate is A because, when in 24V mode, A is the plate that will power the rig with one single battery. Mounting a single battery elsewhere on the rig in this mode will not power it. In Tiffen rigs (current 12/24 Flyer, Archer, Clipper, and Ultra models), this is the plate that faces to the rear when the rig is collapsed for packing. Deployed, it is the rear/lower plate.

The danger arises if you place a TX on the B plate in 24V mode. In this case, the ground the TX will receive is floating at 12V. This ground is connected to the video ground, and that will send that 12V up places where the sun don’t shine. The simple rule is to never mount a TX on the B battery plate. Even in the ‘safety’ of 12V mode, all it will take is a careless flick of a switch to cause pretty coils of blue smoke to rise, followed by interminable phone calls to your insurance agent.

Since many of us take a James Bondian approach to saying never, I include a table listing the 12 possible combinations of one or two batteries and transmitter on the two plates in both series and parallel.

Attached File  Steadicam_Battery_Wiring.png   59.44KB   92 downloads
I 12V—both batteries in parallel.
II 12V—‘A’ battery only active. 24V—both batteries in series.

Fry safe,

Chris
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#2 Matteo Quagliano

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Posted 17 November 2009 - 10:42 AM

"Since many of us take a James Bondian approach to saying never"

:lol:

Thanks for the good review, as for the Archer 12v with one plate only? good to have the TX in between?
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#3 chris fawcett

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Posted 17 November 2009 - 10:50 AM

Thanks for the good review, as for the Archer 12v with one plate only? good to have the TX in between?

No problem at all, though it might make your rig a little back heavy. You can add weight out the monitor bracket to compensate.

You're very welcome,

Chris
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#4 Joel San Juan SOC

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Posted 17 November 2009 - 11:15 AM

Hi Chris,

Yup I recently fried my Wevi Cam Wave doing that. Kinda wireless-less now. Was so thankful it didn't destroy my sled.
Wish I had came across similar advice earlier. But thanks for the explaination, it has made things clearer.

Regards
Joel
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#5 thomas-english

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Posted 17 November 2009 - 05:35 PM

That is a really well explained post. Thank you very much. I assume this is true for MK-V rigs.

Cheers
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#6 chris fawcett

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Posted 17 November 2009 - 05:57 PM

Thanks Thomas!

I think it is true for all rigs, except ones with 24V batteries that step down to 12V. It's easily checked with a meter.

It's also true for power drawn from B-battery plate D-Taps. That's why there are no D-Taps on the Tiffen Steadicam B-battery plates.

Good luck,

Chris
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#7 Jason Torbitt

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Posted 18 November 2009 - 06:48 AM

It also makes a lot more sense to have the TX as high as possible - therefore clearing the vast majority of obstructions that will occur at the lower level, and will guarantee a much cleaner line-of-sight to the RX / video village.
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